Miwa Goto

Adaptive Optics Spectroscopy of the [Fe II] Outflow from DG Tauri

We present results of the velocity-resolved spectroscopy of the [Fe ii] � 1.644 lm emission line along the optical jet emanating from DG Tau. The slit spectrum, obtained with the Subaru Telescope adaptive optics system at an angular resolution of 0>16, shows strong, entirely blueshifted emission on the southwest side of the star. A faint, redshifted counterfeature was also detected on the northeast side with emission within 0>7 of the star being occulted by the circumstellar disk. The blueshifted emission has two distinct radial velocity components. The low-velocity component (LVC) has a peak radial velocity of �� 100 km s � 1 with a FWHM line width of � 100 km s � 1 , and it peaks at 0>2–0>5 from the star. The high-velocity component (HVC) peaks at 0>6–0>8 away from the star, showing a peak radial velocity of �� 220 km s � 1 with a line width of � 50 km s � 1 . These characteristics are remarkably similar to the [Fe ii] outflow from L1551 IRS 5, although the linear scales of the HVCs and LVCs are different for the two objects. We conclude, as an analogy to the case of L1551 IRS 5, that the HVC is a well-collimated jet launched from the region close to the star and that the LVC is a disk wind with a wide opening angle. Detailed comparison of emission parameters between the two sources, however, suggests that part of the LVC emission from DG Tau arises from the gas entrained and accelerated by the HVC, if we assume continuous steady state outflows. The presence of two distinct emission components clearly separated in space and velocity may favor theoretical models with two outflows: one is the LVC magnetohydrodynamically driven near the inner edge of an accretion disk, and the other is the HVC driven by the reconnection of dipolar stellar magnetic fields anchored to the disk. Subject headings: ISM: Herbig-Haro objects — ISM: individual (DG Tauri, HH 158) — ISM: jets and outflows — stars: formation — stars: pre–main-sequence — techniques: high angular resolution

Subaru Deep Survey I. Near-Infrared Observations

Deep near-infraredimages of a blank 2 � ×2 � section of skynear the galactic north pole taken by Subaru Telescope are presented. The total integration times of the J and Kbands were 12.1 hr and 9.7 hr, resulting in 5 σ limiting magnitudes of 25.1 and 23.5 mag, respectively. The numbers of sources within these limiting magnitudes found with an automated detection procedure are 385 in the J band and 350 in K � . Based on photometric measurements of these sources, we present number count vs. magnitude relations, color vs. magnitude diagrams, size vs. color relationships, etc. The slope of the galaxy number count plotted against the AB magnitude scale is about 0.23 in the 22 to 26 AB magnitude range of both bands. The spatial number density of galaxies as well as the slopes in the faint-end region given by the Subaru Deep Field (SDF) survey are consistent with those given by HST-NICMOS surveys, as expressed on the AB magnitude diagram. Several sources having very large J − Kcolor have been found, including a few Kobjects without detection at J. In addition, a number of faint galactic stars were also

Spatially Resolved 3 Micron Spectroscopy of IRAS 22272+5435: Formation and Evolution of Aliphatic Hydrocarbon Dust in Proto-Planetary Nebulae*

We present medium-resolution 3 lm spectroscopy of the carbon-rich proto–planetary nebula IRAS 22272+5435. Spectroscopy with the Subaru Telescope adaptive optics system revealed a spatial variation of hydrocarbon molecules and dust surrounding the star. The rovibrational bands of acetylene (C2H2) and hydrogen cyanide (HCN) at 3.0 lm are evident in the central star spectra. The molecules are concentrated in the compact region near the center. The 3.3 and 3.4 lm emission of aromatic and aliphatic hydrocarbons is detected at 600–1300 AU from the central star. The separation of spatial distribution between gas and dust suggests that the small hydrocarbon molecules are indeed the source of solid material and that the gas left over from the grain formation is being observed near the central star. The intensity of aliphatic hydrocarbon emission relative to the aromatic hydrocarbon emission decreases with distance from the central star. The spectral variation is well matched to that of a laboratory analog thermally annealed with different temperatures. We suggest that either the thermal process after the formation of a grain or the variation in the temperature in the dust-forming region over time determines the chemical composition of the hydrocarbon dust around the proto–planetary nebula. Subject headings: circumstellar matter — dust, extinction — infrared: ISM — ISM: evolution — stars: AGB and post-AGB — stars: individual (IRAS 22272+5435)

Velocity-resolved [Fe II] Line Spectroscopy of L1551 IRS 5: A Partially Ionized Wind under Collimation around an Ionized Fast Jet*

We present a new [Fe II] λ1.644 μm emission-line image of the L1551 IRS 5 jets and a velocity-resolved spectrum obtained with the Subaru Telescope. In the [Fe II] line image showing two separate jetlike features, a strong and spatially wide [Fe II] emission feature was found elongated along the northern jet at its base. The echelle spectrum taken along this feature shows two prominent velocity components together with underlying pedestal and wing emissions. The entire emission range is blueshifted with respect to the systemic velocity, which shows that the emission originates from an outflow. The high-velocity component (HVC) at VLSR = -300 km s-1, which has a corresponding Hα emission, consistently shows a narrow line width of ~40 km s-1 (deconvolved FWHM value). The low-velocity component (LVC) at VLSR = -100 km s-1, on the other hand, has no corresponding Hα feature and is located spatially closer to the IRS 5 VLA sources (IRS 5 VLA) than is the HVC. The LVC shows broad line widths of 130-160 km s-1 (FWHM) near IRS 5 VLA, while its line width decreases with increasing distance from it. We interpret from these characteristics that the HVC is a spatially narrow, well-collimated ionized stellar jet and that the LVC is a widely opened, partially ionized disk wind that is being collimated as it travels away from the origin. The inclination-corrected velocity of the HVC, 440 km s-1, may imply that the accreting protostar driving the jet is rotating at almost its breakup speed. The LVC has an inclination-corrected wind velocity of ~200 km s-1, suggesting that it is accelerated at the region where the accretion disk is interacting with the stellar magnetic field. The pedestal and red wing features may represent the LVC gas entrained and accelerated by the HVC. It is possible that the two apparently parallel jetlike features seen more than 6 away from the IRS 5 VLA sources are the brightened edges of the partially ionized wind.

CISCO: Cooled Infrared Spectrograph and Camera for OHS on the Subaru Telescope

This paper describes a Cooled Infrared Spectrograph and Camera for OHS (CISCO), mounted on the Nasmyth focus of the Subaru telescope. It is primarily designed as a back-end camera of the OH-Airglow Suppressor (OHS), and is also used as an independent, general-purpose near-infrared camera/spectrograph. CISCO is based on a single 1024x1024 format HgCdTe HAWAII array detector, and is capable of either wide-field imaging of 1.8x1.8 field-of-view or low-resolution spectroscopy from 0.9 to 2.4 um. The limiting magnitudes measured during test observations were found to be J=23.5mag and K=22.4mag (imaging, 1 aperture, S/N=5, 1 hr exposure).

Absorption line survey of H3 + toward the Galactic center sources I. GCS 3-2 and GC IRS3

We present high-resolution (R = 20000) spectroscopy of H + 3 absorption toward the luminous Galactic center sources GCS 3-2 and GC IRS 3. With the efficient wavelength coverage afforded by Subaru IRCS, six absorption lines of H + 3 have been detected in each source from 3.5 to 4.0 µm, three of which are new. In particular the 3.543 µm absorption line of the R(3,3) l transition arising from the metastable (J,K)=(3,3) state has been tentatively detected for the first time in the interstellar medium, where previous observations of H + 3 had been limited to absorption lines from the lowest levels: (J,K )=( 1,0) of ortho-H + 3 and (1,1) of para-H + 3 . The H + 3 absorption toward the Galactic center takes place in dense and diffuse clouds along the line of sight as well as the molecular complex close to the Galactic nucleus. At least four kinematic components are found in the H + 3 absorption lines. We suggest identifications of the velocity components with those of H I ,C O, and H2CO previously reported from radio and infrared observations. H + 3 components with velocities that match those of weak and sharp CO and H2CO lines are attributed to diffuse clouds. Our observation has revealed a striking difference between the absorption profiles of H + 3 and CO, demonstrating that the spectroscopy of H + 3 provides information complementary to that obtained from CO spectroscopy. The tentative detection of the R(3,3) l line and the non-detection of spectral lines from other J> 1 levels provide observational evidence for the metastability of the (3,3) level, which is theoretically expected. This suggests that other metastable J = K levels with higher J may also be populated.

Near-Infrared Adaptive Optics Spectroscopy of Binary Brown Dwarfs HD 130948B and HD 130948C*

We present near-infrared spectroscopy of low-mass companions in a nearby triple system HD 130948 (Gliese 564, HR 5534). Adaptive optics on the Subaru Telescope allowed spectroscopy of the individual components of the 0.13 binary system. Based on a direct comparison with a series of template spectra, we determined the spectral types of HD 130948B and C to be L4 +- 1. If we take the young age of the primary star into account (0.3-0.8 Gyr), HD 130948B and C most likely are a binary brown dwarf system.

Diffraction-Limited 3 μm Spectroscopy of IRAS 04296+3429 and IRAS 05341+0852: Spatial Extent of Hydrocarbon Dust Emission and Dust Evolutionary Sequence*

We present 3 μm spectroscopy of the carbon-rich protoplanetary nebulae IRAS 04296+3429 and IRAS 05341+0852, conducted with the adaptive optics system at the Subaru Telescope. We utilize the nearly diffraction-limited spectroscopy to probe the spatial extent of the hydrocarbon dust emitting zone. We find a hydrocarbon emission core extending up to 100-160 mas from the center of IRAS 04296+3429, corresponding to a physical diameter of 400-640 AU, assuming a distance of 4 kpc. However, we find that IRAS 05341+0852 is not spatially resolved with this instrumentation. The physical extent of these protoplanetary nebulae, along with the reanalyzed data of IRAS 22272+5435 published previously, suggests a correlation between the physical extent of the hydrocarbon dust emission and the spectral evolution of the aliphatic to aromatic features in these post-AGB stars. These measurements represent the first direct test of the proposed chemical synthesis route of carbonaceous dust in the circumstellar environment of evolved stars.

Carbon Isotope Ratio in 12CO/13CO toward Local Molecular Clouds with Near-Infrared High-Resolution Spectroscopy of Vibrational Transition Bands

We report the carbon monoxide isotope ratio in local molecular clouds toward LkHα 101, AFGL 490, and Mon R2 IRS 3. The vibrational transition bands of 12CO ν = 2 ← 0 and 13CO ν = 1 ← 0 were observed with high-resolution near-infrared spectroscopy (R = 23,000) to measure the 12CO/13CO ratio. The isotopic ratios are 12CO/13CO = 137 ± 9 (LkHα 101), 86 ± 49 (AFGL 490), and 158 (Mon R2 IRS 3), which are 1.5-2.8 times higher than the local interstellar medium value of 12CO/13CO = 57 ± 5 from millimeter C18O emission observations. This is not easily explained by saturation of the 13CO absorption. It is also questionable whether the selective photodestruction of 13CO can account for the difference between the Galactic trend and the present observation, because the molecular clouds are with high visible extinction (AV = 10-70 mag), well shielded from destructive FUV radiation. The molecular gas associated with AFGL 490 and Mon R2 IRS 3 consists of multiple temperature components lying in the lines of sight. In the cool component (Tex < 100 K), the excitation temperature of 12CO is twice that of 13CO. We attribute the temperature discrepancy to the photon-trapping effect, which makes the radiative cooling of the main isotopomer less effective.

Imaging and Spatially Resolved Spectroscopy of AFGL 2688 in the Thermal Infrared Region

We present ground-based high-resolution (~03) imaging of AFGL 2688 at L (3.8 μm) and M (4.7 μm). A wealth of structure in the central region is revealed as a consequence of less extinction in the thermal infrared. A clear border in the southern lobe at L corresponds to the edge of the heavily obscured region in visible, indicating that there is a dense material surrounding the central region. The images also show a narrow dark lane oriented to 140° east of north with the normal at 50°. The normal position angle is inconsistent with the optical polar axis (P.A. = 15°) but is aligned to the high-velocity CO components found in the radio wavelength observations. The central star remains invisible at L and M. Several clumpy regions in the north lobe dominate in L and M luminosity. In particular, a pointlike source (peak A) at 05 northeast of the center of the nebula exhibits the highest surface brightness with a very red spectral energy distribution (SED). Based on the almost identical SED at adjacent regions, we suggest that the pointlike source is not self-luminous, as was proposed, but is a dense dusty blob reflecting thermal emission from the central star. We also present spatially resolved slit spectroscopy of the bright dusty blobs. An emission feature at 3.4 μm as well as at 3.3 μm is detected everywhere within our field of view. There is no spatial variation in the infrared emission feature throughout the observed area (02-15, or 240-1800 AU from the central source). The constant flux ratio of the emission feature relative to the continuum is consistent with the view that the blobs are mostly reflecting the light from the central star in the 3 μm region.